# Humidity Temperature Conversion Chart



## DonnieW (Jul 2, 2008)

For those of you who aren't aware, relative humidity (RH) has a particular gotcha. As the temperature increases, the amount of humidity the air can hold also increases - this has been covered in many posts. The most obvious example of this is the case of a room in which the temperature moves up several degrees during the day and goes back down in the evening/night. As the temp increases, you may notice your RH reading goes down. This might lead one to believe that their humidor is under humidified - not necessarily so. In all likelihood the amount of moisture in the humidor hasn't changed, only the temperature has. 

For example, if you calibrated your humidor to 70% RH while the ambient air was 70 degrees, the relative humidity (RH) at 75 degrees would be approximately 60% - without any changes to the actual moisture in the air whatsoever!! Now, if you then went and added more humidification to compensate, you'd be over-humidifying your stash immensely.

So what's the point? There is none. I just wanted to share the quick reference I use to help me keep my sanity with my many smaller humidors. I had a prof friend from UofT help me calculate all the compensated values for humidity at various temperatures. The chart below provides RH values for 65, 68, 70, 72, and 75 (salt test). The range assumes you calibrated at 70 degrees, and therefore deviances are provided with that in mind. So in simple terms, if you want to maintain 65% humidity for your sticks, refer to the 65% column. If your meter reads 55% and the rooms is a toasty 75 degrees, don't freak out and add more moisture to your cab - it's all good! This is meant to be a 'good' guideline, but not perfect. There are some assumed values in this calculation, but for all intents and purposes they work for pretty much everyone.


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## chip (Jan 18, 2006)

*Re: Humidity Temperature Conversion*

This has been beat to death so many times, but I guess every now and again it is good to revisit it.

Total :BS

You want to measure RH, not AH....and this chart (and others like it) over think the issue. Have you ever heard a weatherman qualify his RH with temperature?

Find the RH you like....and keep it there. Temperature swings are to be avoided as much as possible, but bottom line is they don't matter so much.
I have kept cigars in humidors at 78 degrees F (in Texas) with no problems. I have had exactly one cigar hatch 3 beetles, it was a custom rolled that was recently bought at a local shop. I never freeze my cigars, either. Too much work for too little return, I am not convinced home freezers are cold enough to actually kill the beetle eggs.
The dreaded beetles usually require high temp and humidity, so following your chart and trying to keep the same (false) RH (which at least you did not suggest) is a recipe for disaster.


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## O-Danger (Apr 26, 2008)

*Re: Humidity Temperature Conversion*



chip said:


> This has been beat to death so many times, but I guess every now and again it is good to revisit it.
> 
> Total :BS
> 
> ...


 :tpd: I understand the science behind this and still humidity charts are a no go. RH is king. That being said don't stress it. anywhere from 63%-73% and my smokes are doing fine:chk.


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## DonnieW (Jul 2, 2008)

*Re: Humidity Temperature Conversion*



chip said:


> This has been beat to death so many times, but I guess every now and again it is good to revisit it.
> 
> Total :BS
> 
> ...


Its got nothing to do with beetles, etc. that wasn't the spirit of the post at all. Simply converting the numbers for an easy time keeping smokes from being to soggy. I'm at 80 degress in my office, thus setting my humidty to 70% would make my sticks look like wet noodles. I simply calculated the correct value to compensate. I didn't find any charts here so I put it up. Nonetheless thanks for humoring yet another thread


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## NCRadioMan (Feb 28, 2005)

*Re: Humidity Temperature Conversion*



DonnieW said:


> I didn't find any charts here so I put it up.


Because they have been de-bunked. 70% rh is 70% rh no matter the temp.


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## DonnieW (Jul 2, 2008)

*Re: Humidity Temperature Conversion*



O-Danger said:


> ...anywhere from 63%-73% and my smokes are doing fine:chk.


 I rest my case!


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## chip (Jan 18, 2006)

*Re: Humidity Temperature Conversion*



DonnieW said:


> Its got nothing to do with beetles, etc. that wasn't the spirit of the post at all. Simply converting the numbers for an easy time keeping smokes from being to soggy. I'm at 80 degress in my office, thus setting my humidty to 70% would make my sticks look like wet noodles. I simply calculated the correct value to compensate. I didn't find any charts here so I put it up.


Untrue....what the chart calculates is the RH needed at a specific temperature to keep the same AH (absolute humidity).
AH is not something to concern yourself with.
70% RH is too high in my opinion, anyway. Others here find it just perfect, it's all up to your preference. Temperature has nothing to do with it.

And I understand the spirit of wanting to share knowledge, I am not trying to be a wanker....although it would not be the first time I appear to be...:r


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## DonnieW (Jul 2, 2008)

*Re: Humidity Temperature Conversion*



NCRadioMan said:


> 70% rh is 70% rh no matter the temp.


That's absolutely correct. But the actual water in the air is completely different.


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## chip (Jan 18, 2006)

*Re: Humidity Temperature Conversion*



DonnieW said:


> That's absolutely correct. But the actual water in the air is completely different.


And so is the evaporation and absorption rates of medium. Which is why cigars do well at a fixed RH.


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## DonnieW (Jul 2, 2008)

*Re: Humidity Temperature Conversion*



chip said:


> Untrue....what the chart calculates is the RH needed at a specific temperature to keep the same AH (absolute humidity).
> AH is not something to concern yourself with.
> 70% RH is too high in my opinion, anyway. Others here find it just perfect, it's all up to your preference. Temperature has nothing to do with it.
> 
> And I understand the spirit of wanting to share knowledge, I am not trying to be a wanker....although it would not be the first time I appear to be...:r


I haven't come across any wankers here, frankly that's what I like about this place.

Preferences are just that, I completely agree. But temp does play a big part - screw beetles, it's simply the effect on humidity. If temp had no effect on things, you'd be taking it in the a$$ at the gas pump even more than we are now - i.e. volume correction. I can explain molecular composition of warm air versus cooler air if anyone wants to know, and how it affects humidity. But I don't want to digress. 

Like O-Danger said, between such a wide spread his smokes are just fine... That's ALL I wanted to re-enforce with this post. Seems like I've read a million threads with people freaking about swings in their RH readings and spending needless time worrying about it.


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## NCRadioMan (Feb 28, 2005)

*Re: Humidity Temperature Conversion*

Here are few threads about the infamous chart:

http://www.clubstogie.com/vb/showthread.php?t=27771&highlight=humidity+chart
http://www.clubstogie.com/vb/showthread.php?t=70858&highlight=humidity+chart
http://www.clubstogie.com/vb/showthread.php?t=30143&highlight=humidity+chart
http://www.clubstogie.com/vb/showthread.php?t=19658&highlight=humidity+chart

Also, here a good read on water vapor myths in case anyone is interested. Thanks for the link, poker! http://www.meto.umd.edu/~stevenb/vapor/


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## DonnieW (Jul 2, 2008)

Man... I'm gonna take it in the _ass_ on this one aren't I :r


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## NCRadioMan (Feb 28, 2005)

DonnieW said:


> Man... I'm gonna take it in the _ass_ on this one aren't I :r


Nah! I think alot of folks will learn alot from this thread and that is what it's all about. :tu


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## chip (Jan 18, 2006)

*Re: Humidity Temperature Conversion*



DonnieW said:


> I haven't come across any wankers here, frankly that's what I like about this place.
> 
> Preferences are just that, I completely agree. But temp does play a big part - screw beetles, it's simply the effect on humidity. If temp had no effect on things, you'd be taking it in the a$$ at the gas pump even more than we are now - i.e. volume correction. I can explain molecular composition of warm air versus cooler air if anyone wants to know, and how it affects humidity. But I don't want to digress.
> 
> Like O-Danger said, between such a wide spread his smokes are just fine... That's ALL I wanted to re-enforce with this post. Seems like I've read a million threads with people freaking about swings in their RH readings and spending needless time worrying about it.


I am an engineer (some here have a greater knowledge of chemistry, but some "experts" spout pure bunk), and although everything you have said is correct, MY POINT is you have not considered everything. There is that whole pesky air/medium interface to consider.
And you are right about gas, I believe pumps are calibrated at 72 degrees or so, and since they measure gallons indirectly by volume, we get less than a gallon if the temperature is higher than the calibration temperature.

I can't believe I have posted this much on a single thread, or even a single evening....:r

Lively conversation....enjoy a good smoke, my friend!!


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## NCRadioMan (Feb 28, 2005)

*Re: Humidity Temperature Conversion*



chip said:


> I can't believe I have posted this much on a single thread, or even a single evening....:r


You're not the only one, ole buddy. :r :tu


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## chip (Jan 18, 2006)

*Re: Humidity Temperature Conversion*



NCRadioMan said:


> You're not the only one, ole buddy. :r :tu


Might as well whore it up and reach 1000.....not bad for 2 and 1/2 years, eh?


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## DonnieW (Jul 2, 2008)

*Re: Humidity Temperature Conversion*



chip said:


> I can't believe I have posted this much on a single thread, or even a single evening....:r


At least I helped you break 1000 posts. Congrats!!

[EDIT] Does that make me a pimp?


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## Good_Stogies (Jun 5, 2008)

DonnieW, If I understand what you are saying correctly you are talking about short term temperature swings, say less than 24 hrs. If so then I completely agree that you will see a flux in rh and the chart you provided should come pretty close predicting what these changes will be. I also agree that these changes are nothing to fret about and you would run your self crazy trying to compensate for them. More or less just some thing to be aware of. On the other hand I also see and agree (and it looks like you do to) with what the others are saying in terms of long term stabile temperature and the fact that there is no need for any sort of humidity compensation no mater what temp you keep your smokes at. It would be great if we all could keep our cigars under laboratory conditions and rock solid temperatures but unfortunately that is not the case and some will have to store there cigars in a place that sees somewhat rapid temperature change and with that change will come a change in the indicated relative humidity because the amount of moisture in the air remains pretty much the same. I may be wrong but this looks like more of a misunderstanding than a disagreement. The important part is at the end of the day we still have some great cigars to enjoy and great company to enjoy them with! :ss


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## ChasDen (Dec 12, 2007)

I've seen this conversation pop up several times during my brief membership here and it makes my head hurt every time. The thing I take out, it for what it's worth is what we are looking for is "Moisture Content" The way we measure that content is with a device that measures relative humidity in the surrounding air. This device reads differently depending on the air temperature it's in. Without starting a whole new debate, the common setting most of us see is 70/70. If that's correct then there is a specific amount of water in the cigar at that point. In a controlled environment we could assume that X amount of water is present at that point. If we changed only the temperature, the reading on our device would change but the amount of water would not. Assuming that is correct. The changes we see in our everyday storage solutions need to take that into account. I think the biggest problem new smokers find is the need to maintain a specific RH at no matter what temperature they have. Thus the numerous threads on people struggling to maintain a specify RH all the time. If you find that your stuff smokes best at 65 and the temperature fluctuates, stop adding and subtracting water to try to keep it at dead on 65 every minute of the day. Assuming temperature swings in a 48 to 72 hour period there are bound to be swings in the RH reading, but is the moisture content changing? In my opinion the chart may help you understand that although your device is changing, perhaps the water content is not. 

And isn't that what we are really after in the long run, water content?

Chas


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## Scimmia (Sep 22, 2006)

ChasDen said:


> Assuming temperature swings in a 48 to 72 hour period there are bound to be swings in the RH reading, but is the moisture content changing? In my opinion the chart may help you understand that although your device is changing, perhaps the water content is not.


Damnit, I was really trying to stay out of this thread.

The answer here is that yes, the moisture content of the cigar is changing. To put it simply, as the temperature rises, more water is evaporating out of your cigars, so you need more water in the air to replace it. This is why keeping a constant amount of moisture in the air won't give you the results you want.


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## lenguamor (Nov 23, 2006)

*Re: Humidity Temperature Conversion*



NCRadioMan said:


> Because they have been de-bunked. 70% rh is 70% rh no matter the temp.


True that. That's why it's called _relative_ humidity.

Your hygrometer will show the RH without having to resort to quantum physics to try and figure it all out.


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## lenguamor (Nov 23, 2006)

DonnieW said:


> Man... I'm gonna take it in the _ass_ on this one aren't I :r


:r You shouldn't. Any effort made in good faith shouldn't.


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## DonnieW (Jul 2, 2008)

ChasDen said:


> I've seen this conversation pop up several times during my brief membership here and it makes my head hurt every time. The thing I take out, it for what it's worth is what we are looking for is "Moisture Content" The way we measure that content is with a device that measures relative humidity in the surrounding air. This device reads differently depending on the air temperature it's in. Without starting a whole new debate, the common setting most of us see is 70/70. If that's correct then there is a specific amount of water in the cigar at that point. In a controlled environment we could assume that X amount of water is present at that point. If we changed only the temperature, the reading on our device would change but the amount of water would not. Assuming that is correct. The changes we see in our everyday storage solutions need to take that into account. I think the biggest problem new smokers find is the need to maintain a specific RH at no matter what temperature they have. Thus the numerous threads on people struggling to maintain a specify RH all the time. If you find that your stuff smokes best at 65 and the temperature fluctuates, stop adding and subtracting water to try to keep it at dead on 65 every minute of the day. Assuming temperature swings in a 48 to 72 hour period there are bound to be swings in the RH reading, but is the moisture content changing? In my opinion the chart may help you understand that although your device is changing, perhaps the water content is not.
> 
> And isn't that what we are really after in the long run, water content?
> 
> Chas


That is put much more eloquently than I could ever do - I would rather people reference your dialogue than mine. It's simply well put.

My chart is merely meant to illustrate that there is change in the RH reading as temperatures change - all the while the absolute moisture (gm/m3) in the humidor remains the same. I've witnessed firsthand many people 'chasing' their RH readings trying to add or remove moisture, assuming their humidor is all over the place. In reality, even a cheap humidor or coolerdor will hold a steady moisture content. As a couple others (well regarded members) in this thread have eluded to, don't worry about the movement of the gauge it's simply a reaction to temperature swings.


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## Scimmia (Sep 22, 2006)

DonnieW said:


> As a couple others (well regarded members) in this thread have eluded to, don't worry about the movement of the gauge it's simply a reaction to temperature swings.[/FONT][/COLOR]


Yes, the "movement of the gauge" is in reaction to temperature swings, but that doesn't mean that it doesn't have an effect on your cigars.


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## shaggy (Dec 28, 2006)

Scimmia said:


> Damnit, I was really trying to stay out of this thread.
> 
> The answer here is that yes, the moisture content of the cigar is changing. To put it simply, as the temperature rises, more water is evaporating out of your cigars, so you need more water in the air to replace it. This is why keeping a constant amount of moisture in the air won't give you the results you want.


i knew doug couldnt stay out of this....:r


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## sailchaser (Jun 16, 2007)

shaggy said:


> i knew doug couldnt stay out of this....:r


Shaggy neither could you or I and I agree with Chip that each person likes their smokes the way the like it,I would have never had a 60% humi before but tried it after some long conservations with Chip and I do have one now and I have certain sticks that I keep in there and love the taste it produces:2


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## Scimmia (Sep 22, 2006)

shaggy said:


> i knew doug couldnt stay out of this....:r


shup mike.

:ss


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## chip (Jan 18, 2006)

sailchaser said:


> Shaggy neither could you or I and I agree with Chip that each person likes their smokes the way the like it,I would have never had a 60% humi before but tried it after some long conservations with Chip and I do have one now and I have certain sticks that I keep in there and love the taste it produces:2


Yer kidding, right?
No one ever listens to me.....

See ya in a few days....it's such a long trip over to yer place...:r


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